Adhesives - Used By and Against Criminals

Sometimes I am really amazed how adhesives have permeated almost every aspect of life. Even certain undesirable aspects such as the criminal element have discovered the many uses for adhesives. Much of this criminal use is in tape form. By far the commonest tape found as evidence in two out of three criminal cases is duct tape. It has been used from packaging of drugs, as a gag and ligature, and in disposal of murder victims. The next most common tape as evidence is vinyl electric tape, usually in explosive devices.

Because of the variability of tape products, the analysis and comparison of tape evidence in the forensic science laboratory can provide valuable information. Some classes of tape exhibit more variability than others. In general, the more complex the product (e.g., duct tape), the more variable it is. This is good for the forensic scientist and bad for the criminal since almost every roll of tape has discrete and specific "markers".

Several adhesive tape databases have been constructed for the forensic scientist to help in these tasks. For example, the Pressure Sensitive Tape Council maintains a directory of thousands of different commercial adhesive tapes. Also analytical databases are being developed to help identify the adhesive type, backing materials, and other material characteristics of the tape. ATR infrared spectroscopy is one tool used to do this.

Although criminals may use adhesives in their nefarious activities, criminologists can use adhesives to identify the criminal. The most well-known example of this is the use of cyanoacrylate adhesive in a process called "fuming" to recover latent fingerprints. By now any one with a television must have seen a criminologist busy at work uncovering latent fingerprints left behind at the crime scene.

I have always wanted to know if this process is as complicated as it looks on TV. Surprisingly it is not. You do not need technologically advanced forensic equipment, the process is relatively safe, and you can find the components generally in your own home.

The following steps are a "how-to-guide" for anyone interested in fuming fingerprints or for budding criminologists.²

1. Shape a piece of aluminum foil into the size of a small bowl with a flat bottom and straight sides.
2. Place a cardboard box with the open ends at the top and bottom. Fold out the top flaps so that you can work inside the box. Make sure that the bottom flaps are folded together and secured. Tape the bottom shut for the best results.
3. Cut a hole in one of the box's bottom corners large enough for a coffee cup warmer to go into the box and feed the plug through the hole. Plug the coffee cup warmer into an outlet.
4. Add hot water to a coffee cup and place it inside the box. Do not place it on the coffee cup warmer.
5. Tear a small square piece of foil from your roll of aluminum. Rub your thumb on the forehead and then press your thumb to a foil square. This is your control print. Place it inside the box.
6. Squirt a coin-sized drop of cyanoacrylate onto the center of the tray described in step 1. Place the foil tray in the box. Turn on the coffee cup warmer.
7. Close the box's top flaps. Wait 10 minutes before opening the box to check on the progress. If your test print turns white, you've completed the process. If it has not turned white, wait another 10 minutes.

So, as with most technologies, adhesives can be used to commit crimes as well as in solving them. I guess it has to do with something about the balance of power.